The following line passes through point $(4, 9)$ : $y = \dfrac{5}{4} x + b$ What is the value of the $y$ -intercept $b$ ?
Answer: Substituting $(4, 9)$ into the equation gives: $9 = \dfrac{5}{4} \cdot 4 + b$ $9 = 5 + b$ $b = 9 - 5$ $b = 4$ Plugging in $4$ for $b$, we get $y = \dfrac{5}{4} x + 4$. ${1}$ ${2}$ ${3}$ ${4}$ ${5}$ ${6}$ ${7}$ ${8}$ ${9}$ ${10}$ ${\llap{-}2}$ ${\llap{-}3}$ ${\llap{-}4}$ ${\llap{-}5}$ ${\llap{-}6}$ ${\llap{-}7}$ ${\llap{-}8}$ ${\llap{-}9}$ ${\llap{-}10}$ ${1}$ ${2}$ ${3}$ ${4}$ ${5}$ ${6}$ ${7}$ ${8}$ ${9}$ ${10}$ ${\llap{-}2}$ ${\llap{-}3}$ ${\llap{-}4}$ ${\llap{-}5}$ ${\llap{-}6}$ ${\llap{-}7}$ ${\llap{-}8}$ ${\llap{-}9}$ ${\llap{-}10}$ $(4, 9)$